Paradigm shift in Nutrient-Energy-Water centered sustainable wastewater treatment system through synergy of bioelectrochemical system and anaerobic digestion.

With advancements in research and the necessity of improving the performance of bioelectrochemical system (BES), coupling anaerobic digestion (AD) with BES is crucial for energy gain from wastewater and bioremediation. Hybridization of BES-AD concept opens new avenues for pollutant degradation, carbon capture and nutrient-resource recovery from wastewater. The strength of merging BES-AD lies in synergy, and this approach was employed to differentiate fads from strategies with the potential for full-scale implementation and making it an energy-positive system. The integration of BES and AD system increases the overall performance and complexity of combined system and the cost of operation. From a technical standpoint, the primary determinants of BES-AD feasibility for field applications are the scalability and economic viability. High potential market for such integrated system attract industrial partners for more industrial trials and investment before commercialization. However, BES-AD with high energy efficacy and negative economics demands performance boost.

Release of phosphorus through pretreatment of waste activated sludge differs essentially from that of carbon and nitrogen resources: Comparative analysis across four wastewater treatment facilities.

The accumulation of phosphorus in activated sludge in wastewater treatment plants (WWTPs) provides potential for phosphorus recovery from sewage. This study delves into the potential for releasing phosphorus from waste activated sludge through two distinct treatment methods-thermal hydrolysis and pH adjustment. The investigation was conducted with activated sludge sourced from four WWTPs, each employing distinct phosphorus removal strategies. The findings underscore the notably superior efficacy of pH adjustment in solubilizing sludge phosphorus compared to the prevailing practice of thermal hydrolysis, widely adopted to enhance sludge digestion. The reversibility of phosphorus release within pH fluctuations spanning 2 to 12 implies that the release of sludge phosphorus can be attributed to the dissolution of phosphate precipitates. Alkaline sludge treatment induced the concurrent liberation of COD, nitrogen, and phosphorus through alkaline hydrolysis of sludge biomass and the dissolution of iron or aluminium phosphates, offering potential gains in resource recovery and energy efficiency.

Aviation fuel based on wastewater-grown microalgae: Challenges and opportunities of hydrothermal liquefaction and hydrotreatment.

The current technical issues related to the conversion of algal biomass into aviation biofuel through hydrothermal liquefaction (HTL) and the upgrading of bio-oil through hydrotreatment have been reviewed and consolidated. HTL is a promising route for converting microalgae into sustainable aviation fuel (SAF). However, HTL must be followed by the hydrotreatment of bio-oil to ensure that its composition and properties are compatible with SAF standards. The fact that microalgae offer the possibility of recovering wastewater treatment resources not only makes them more attractive but also serves as an incentive for wastewater treatment, especially in countries where this service has not been universalized. The combination of SAF and wastewater treatment aligns with the Sustainable Development Goals of the United Nations, representing an advantageous opportunity for both aviation and sanitation. In this context, the utilization of HTL by-products in the concept of a biorefinery is essential for the sustainability of aviation biofuel production through this route. Another important aspect is the recovery and reuse of catalysts, which are generally heterogeneous, allowing for recycling. Additionally, discussions have focused on biomass pretreatment methods, the use of solvents and catalysts in HTL and hydrotreatment reactions, and the operational parameters of both processes. All these issues present opportunities to enhance the quantity and quality of bio-oil and aviation biofuel.

Effect of iron sources on methane production and phosphorous transformation in an anaerobic digestion system of waste activated sludge.

The iron materials are commonly employed to enhance resource recovery from waste activated sludge through anaerobic digestion (AD). The influence of different iron sources, such as Fe2O3, Fe3O4, and FeCl3 on methane production and phosphorus transformation in AD systems with thermal hydrolyzed sludge as the substrate was assessed in this study. The results indicated that iron oxides effectively promote methane yield and methane production rate in AD systems, resulting in a maximum increase in methane production by 1.6 times. Soluble FeCl3 facilitated the removal of 92.3% of phosphorus from the supernatant through the formation of recoverable precipitates in the sludge. The introduction of iron led to an increase in the abundance of bacteria responsible for hydrolysis and hydrogenotrophic methanogenesis. However, the enrichment of microbial communities varied depending on the specific irons used. This study provides support for AD systems that recover phosphorus and produce methane efficiently from waste sludge.

Phosphorus mining from marine sediments adopting different carbon/nitrogen strategies driven by anaerobic reactors: The exploration of potential mechanism and microbial activities.

To investigate the possibility of phosphorus (P) recovery from marine sediment and explore the role of the carbon: nitrogen ratio in affecting the internal P release under anaerobic conditions, we experimented with the external addition of carbon (acetic acid and glucose) and ammonia nitrogen (NH4-N) to expose P release mechanisms. The 24-day anaerobic incubations were conducted with four different carbon: nitrogen dosing groups including no NH4-N addition and COD/N ratios of 100, 50, and 10. The P release showed that extra NH4-N loading significantly suppressed the decomposition of P (p < 0.05) from the marine sediment, the maximum P release was 4.07 mg/L and 7.14 mg/L in acetic acid- and glucose-fed systems, respectively, without extra NH4-N addition. Additionally, the results exhibited that the imbalance of carbon: nitrogen not only failed to induce the production of organic P mineralization enzyme (alkaline phosphatase) in the sediment but also suppressed its activity under anaerobic conditions. The highest enzyme activity was observed in the group without additional NH4-N dosage, with rates of 1046.4 mg/(kg∙h) in the acetic acid- and 967.8 mg/(kg∙h) in the glucose-fed system, respectively. Microbial data analysis indicated that a decrease in the abundance of P release-regulating bacteria, including polyphosphate-accumulating organisms (Rhodobacteraceae) and sulfate-reducing bacteria (Desulfosarcinaceae), was observed in the high NH4-N addition groups. The observed reduction in enzyme activity and suppression of microbial activity mentioned above could potentially account for the inhibited P decomposition in the presence of high NH4-N addition under anaerobic conditions. The produced P-enriched solution from the bioreactors may offer a promising source for future recovery endeavors.

Enhancing the nitrogen and phosphorus content of faecal-derived biochar via adsorption and precipitation from human urine.

Urine diversion in toilets is a promising strategy to maximise nutrient recovery and produce low-cost urine-derived fertilisers. There are various methods for nutrient recovery from urine, including precipitation and adsorption onto porous media, such as biochars. This study uses faecal-derived biochars to produce and, for the first time, comprehensively characterise enriched biochar fertilisers with the addition of fully hydrolysed undiluted human urine. The evolution of urea hydrolysis and nutrient content during urine storage was initially investigated over a 6-month storage period and NH4+ adsorption mechanisms studied under varying biochar doses and NH4-N concentrations. The process was further optimised by adding MgO to induce precipitation reactions, enabling the combined recovery of NH4+ and P. For NH4+ adsorption, experimental data exhibited a good fit to both the Freundlich (R2 = 0.989) and Langmuir (R2 = 0.974) isotherm models and the rate of the reaction was well described by a pseudo 2nd order kinetics model (R2 = 0.988). The NH4+ uptake was rapid during the initial 2 h of the reaction and the adsorption process reached completion after 24 h. The NH4-N adsorption capacity of the faecal-derived biochar was 19.8 mg/g and the main adsorption mechanism identified was ion exchange (K+ ↔ NH4+), as confirmed by XRD and ICP-OES. The effect of different biochar doses (0, 25, 50, 100 g/L) and MgO addition scenarios (Mg:P = 0, 1.5, 4) on N and P recovery showed that the combination of MgO (Mg:P = 1.5) with the lower biochar dose (25 g/L) produced the most NP-rich fertiliser product which was easily separated from the urine. Faecal-derived biochar had a limited adsorption capacity for P, with precipitation being the main mechanism for P recovery. When MgO was added to urine, >98% of total P was recovered via precipitation of struvite/struvite-K and substituted hydroxyapatite, as identified via SEM-EDX. Faecal-derived biochar was a successful carrier to recover the P-containing precipitates and facilitate liquid-solid separation after treatment. The findings of this study provide proof-of concept for the systemic management of source separated human excreta and pave the way for the production of marketable waste-derived fertilisers from on-site sanitation systems.

Novel process for organic wastewater treatment using aerobic composting technology: Shifting from pollutant removal towards resource recovery.

In this study, an organic wastewater treatment process based on aerobic composting technology was developed in order to explore the transition of wastewater treatment from pollutants removal to resource recovery. The novelty of the process focuses towards the microbial metabolic heat that is often ignored during the composting, and taking advantage of this heat for wastewater evaporation to achieve zero-discharge treatment. Meanwhile, this process can retain the wastewater's nutrients in the composting substrate to realize the recovery of resources. This study determined the optimum condition for the process (initial water content of 50 %, C/N ratio of 25:1, ventilation rate of 3 m3/h), and 69.9 % of the total heat generated by composting was used for wastewater treatment under the condition. The HA/FA ratio of composting substrate increased from 0.07 to 0.53 after wastewater treatment, and the retention ratio of TOC and TN was 52.3 % and 61.7 %, respectively, which proved the high recycling value of the composting products. Thermoduric and thermophilic bacteria accounted for 44.3 % of the community structure at the maturation stage, which played a pivotal role in both pollutant removal and resource recovery.

Biological Activities of Citrus aurantium Leaf Extract by Optimized Ultrasound-Assisted Extraction.

Several studies have explored the biological activities of Citrus aurantium flowers, fruits, and seeds, but the bioactivity of C. aurantium leaves, which are treated as waste, remains unclear. Thus, this study developed a pilot-scale ultrasonic-assisted extraction process using the Box-Behnken design (BBD) for the optimized extraction of active compounds from C. aurantium leaves, and their antityrosinase, antioxidant, antiaging, and antimicrobial activities were evaluated. Under optimal conditions in a 150× scaleup configuration (a 30 L ultrasonic machine) of a pilot plant, the total phenolic content was 69.09 mg gallic acid equivalent/g dry weight, which was slightly lower (3.17%) than the theoretical value. The half maximal inhibitory concentration of C. aurantium leaf extract (CALE) for 2,2-diphenyl-1-picrylhydrazyl-scavenging, 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid)-scavenging, antityrosinase, anticollagenase, antielastase and anti-matrix metalloprotein-1 activities were 123.5, 58.5, 181.3, 196.4, 216.3, and 326.4 mg/L, respectively. Moreover, the minimal inhibitory concentrations for bacteria and fungi were 150-350 and 500 mg/L, respectively. In total, 17 active compounds were detected in CALE-with linalool, linalyl acetate, limonene, and α-terpineol having the highest concentrations. Finally, the overall transdermal absorption and permeation efficiency of CALE was 95.9%. In conclusion, our CALE demonstrated potential whitening, antioxidant, antiaging, and antimicrobial activities; it was also nontoxic and easily absorbed into the skin as well as inexpensive to produce. Therefore, it has potential applications in various industries.

Enhanced biological wastewater treatment supplemented with anaerobic fermentation liquid of primary sludge.

The wastewater treatment performance in an inverted A2/O reactor supplemented with fermentation liquid of primary sludge was explored comparing to commercial carbon sources sodium acetate and glucose. Similar COD removal rate was observed with the effluent COD stably reaching the discharge standard for those 3 carbon sources. However, the fermentation liquid distributed more carbon source in the anaerobic zone. Fermentation liquid and sodium acetate tests achieved better nitrogen removal rate than glucose test. The fermentation liquid test showed the best biological phosphorus removal performance with the effluent phosphorus barely reaching the discharge standard. The microbial community characterization revealed that the fermentation liquid test was dominated by phylum Proteobacter in all the anoxic, anaerobic and aerobic zones. Denitrifying phosphorus accumulating organisms (PAOs) (i.e., genera Dechloromonas and unclassified_f__Rhodocyclaceae) were selectively enriched with high abundances (over 20%), which resulted in improved phosphorus removal efficiency. Moreover, the predicted abundances of enzymes involved in nitrogen and phosphorus removal were also enhanced by the fermentation liquid.

Effect of macronutrients (carbon, nitrogen, and phosphorus) on the growth of Chlamydomonas reinhardtii and nutrient recovery under different trophic conditions.

More stringent discharge standards have led to the development of an alternative nutrient recovery system from wastewater. Microalgae cultivation in wastewater treatment works has presented considerable promise from the perspective of sustainable resource management. Growth kinetics models are useful tools to optimize nutrient recovery from wastewater by algal uptake. Therefore, this research aims to identify the growth kinetics of Chlamydomonas reinhardtii under both heterotrophic and phototrophic conditions with different nutrient concentrations that typify those found in wastewater treatment works. In addition, the effects of macronutrients (C, N, and P) on heterotrophic and phototrophic microalgae growth and nutrient recovery were studied. Greater specific growth rates were achieved under heterotrophic conditions than in phototrophic cultivation. The maximum specific growth rates and nutrient recovery efficiencies were achieved at 5 mg P L-1 under both heterotrophic and phototrophic growth conditions. Nitrate was the preferred form of nitrogen source under heterotrophic conditions, while nitrogen sources did not present any significant influences in the phototrophic cultivation. Specific growth rates reported for both heterotrophic and phototrophic microalgae at lower carbon concentrations (3.10 d-1 and 0.46 d-1, sequentially) were higher than those at higher carbon concentrations (1.95 d-1 and 0.22 d-1, respectively). C. reinhardtii presented an extreme capacity to adapt and grow at all experimental conditions tested in heterotrophic and phototrophic cultivations.

Ingenious use of autocatalytic hydrodeoxygenation for the separation and recovery of oil and iron from rolling oil sludge.

This paper introduces a transformative hydrodeoxygenation process for the simultaneous recovery of oil and iron from hazardous rolling oil sludge (ROS). Leveraging the inherent catalytic capabilities of iron/iron oxide nanoparticles in the sludge, our process enables the conversion of fatty acids and esters into hydrocarbons under conditions of 4.5 MPa, 330 °C, and 500 rpm. This reaction triggers nanoparticle aggregation and subsequent separation from the oil phase, allowing for effective resource recovery. In contrast to conventional techniques, this method achieves a high recovery rate of 98.3% while dramatically reducing chemical reagent consumption. The reclaimed petroleum and iron-ready for high-value applications-are worth 3910 RMB/ton. Moreover, the process facilitates the retrieval of nanoscale magnetic Fe and Fe0 particles, and the oil, with an impressive hydrocarbon content of 87.8%, can be further refined. This energy-efficient approach offers a greener, more sustainable pathway for ROS valorization.

Modeling National Embedded Phosphorus Flows of Corn Ethanol Distillers' Grains to Elucidate Nutrient Reduction Opportunities.

Freshwater quality and ecosystem impairment associated with excess phosphorus (P) loadings have led to federally mandated P reduction for certain organic waste streams. Phosphorus reduction from livestock and poultry feeds such as corn ethanol distillers' grains (DGs) presents a centralized strategy for reducing P loss from animal manurein agriculturally intensive states, but little is known about the actual distribution and geospatial P contributions of DGs as animal feed. Here, a county-level flow network for corn ethanol DGs was simulated in the United States to elucidate opportunities for P reduction and the potential for nutrient trading between centralized sources. Overall, the estimated P in DGs that was transferred to US animal feeding operations was nearly twice that present in all human waste prior to treatment. Simulation results suggest that Midwestern states account for an estimated 63% of domestic DG usage, with 72% utilized within the state of production. County-level data were also used to highlight the potential of using nutrient trading markets to incentivize P recovery from DGs at biorefineries within an agriculturally intensive watershed region in Iowa. In summary, corn ethanol biorefineries represent a key leverage point for sustainable P management at the national and local scales.

Performance and mechanisms of urea exposure for enhancement of biotransformation of sewage sludge into volatile fatty acids.

Herein, a cost-effective method for improving the anaerobic fermentation performance of sewage sludge (SS) is proposed. The highest volatile fatty acids (VFAs) reached up to 5550 mg COD/L with the supplementation of 0.2 g urea/g total suspended solids (TSS). Intensive exploration showed that SS decomposition was profoundly triggered by urea and the free ammonia generated due to the hydrolysis of urea, providing adequately bioaccessible substrates for acidogenic reactions and thus contributing to VFAs formation. Microbial composition analysis indicated that functional bacteria (i.e., Tissierella and Clostridium) associated with VFAs generation were enriched. Moreover, the metabolic activities of functional flora (i.e., membrane transport and fatty acid synthesis) were up-regulated due to the stimulation of urea. In general, the increase in bioavailable organic matter and functional microbes, and thus the increased microbial metabolic activities, improved the efficient production of VFAs. This study could provide a cost-effective approach for resource recovery from SS.

Continuous cultivation of microalgae yields high nutrient recovery from nitrified urine with limited supplementation.

Microalgae can play a key role in the bioeconomy, particularly in combination with the valorisation of waste streams as cultivation media. Urine is an example of a widely available nutrient-rich waste stream, and alkaline stabilization and subsequent full nitrification in a bioreactor yields a stable nitrate-rich solution. In this study, such nitrified urine served as a culture medium for the edible microalga Limnospira indica. In batch cultivation, nitrified urine without additional supplements yielded a lower biomass concentration, nutrient uptake and protein content compared to modified Zarrouk medium, as standard medium. To enhance the nitrogen uptake efficiency and biomass production, nitrified urine was supplemented with potentially limiting elements. Limited amounts of phosphorus (36 mg L-1), magnesium (7.9 mg L-1), calcium (12.2 mg L-1), iron (2.0 mg L-1) and EDTA (88.5 mg Na2-EDTA.2H2O L-1) rendered the nitrified urine matrix as effective as modified Zarrouk medium in terms of biomass production (OD750 of 1.2), nutrient uptake (130 mg N L-1) and protein yield (47%) in batch culture. Urine precipitates formed by alkalinisation could in principle supply enough phosphorus, calcium and magnesium, requiring only external addition of iron, EDTA and inorganic carbon. Subsequently, the suitability of supplemented nitrified urine as a culture medium was confirmed in continuous Limnospira cultivation in a CSTR photobioreactor. This qualifies nitrified urine as a valuable and sustainable microalgae growth medium, thereby creating novel nutrient loops on Earth and in Space, i.e., in regenerative life support systems for human deep-space missions.

Volatile fatty acids bio-production using extracellular polymeric substances disengaged from sludge for carbon source recycling.

Excessive waste-activated sludge (WAS) and insufficient carbon source (CS) for biological nitrogen removal (BNR) often coexist in municipal sewage treatment. Although the production of volatile fatty acids (VFAs) from WAS has been recognized as a promising solution, the development is limited by low VFAs production efficiency and dewatering deterioration of sludge. This study extracted the extracellular polymeric substances (EPS) from sludge by low-temperature thermal-hydrolysis (LTH) and high-speed hydro-cyclone (HSHC) pretreatment and recovered it for high-quality VFAs bio-production in thermophilic fermentation. Microbial mechanism analysis disclosed that interspecific interaction networks composed of functional flora, which accumulate VFAs by bio-converting EPS primarily and supplemented by EPS synthesis, guaranteed the efficient bio-production of VFAs. This process scheme shows promise in providing alternative denitrification CSs and avoiding deterioration of sludge dewaterability.

Phosphorus recycling from waste activated sludge using the hydrothermal platform: Recovery, solubility and phytoavailability.

To address the grand challenge of increasing the sustainability of wastewater treatment plants, hydrothermal carbonization was studied as a nutrient recovery platform, transforming sludge into a valuable hydrochar. Carbonization was achieved at different temperatures (200-300 °C) and durations (30-120 min). The highest mass recovery (73%) was observed in the lowest temperature, while the lowest (49%) was obsereved at the highest temperature. Under all reaction conditions, phosphorus recovery values exceeded 80%, with the dominated fraction of inorganic-P in the hydrochar being HCl-extractable. Although HCl-extractable P is considered a moderately labile P fraction, P phytoavailability assays indicate that sewage sludge hydrochar is an excellent source for P, surpassing soluble P, likely due to its slow-release nature. We postulate that polyphosphates constitute a significant portion of this P pool. Overall, we emphasize the benefits of using HTC as a circular economy approach to convert sludge into a valuable hydrochar.

Human urine: A novel source of phosphorus for vivianite production.

Human urine contributes up to 50 % of the phosphorus load in domestic wastewater. Decentralized sanitation systems that separately collect urine provide an opportunity to recover this phosphorus. In this study, we leveraged the unique and complex chemistry of urine in favor of recovering phosphorus as vivianite. We found that the type of urine affected the yield and purity of vivianite, but the kind of iron salt used, and reaction temperature, did not affect the yield and purity. Ultimately, it was the urine pH that affected the solubility of vivianite and other co-precipitates, with the highest yield (93 ± 2 %) and purity (79 ± 3 %) of vivianite obtained at pH 6.0. Yield and purity of vivianite were both maximized when Fe:P molar ratio was >1.5:1, but <2.2:1. This molar ratio provided sufficient iron to react with all available phosphorus, while exerting a competitive effect that suppressed the precipitation of other precipitates. Vivianite produced from fresh urine was less pure than vivianite produced from synthetic urine, because of the presence of organics in real urine, but washing the solids with deionized water improved the purity by 15.5 % at pH 6.0. Overall, this novel work adds to the growing body of literature on phosphorus recovery as vivianite from wastewater.

Life-cycle assessment and techno-economic evaluation of the value chain in nutrient recovery from wastewater treatment plants for agricultural application.

The recovery of nitrogen and phosphorus is important to promote circular economy in wastewater treatment plants (WWTPs). In this study, the life cycle assessment (LCA) and techno-economic assessment (TEA) of a novel pilot-scale plant aimed at recovering ammonium nitrate and struvite for subsequent application in agriculture was conducted. The nutrient recovery scheme was implemented in the sludge line of the WWTP and included (i) struvite crystallisation and (ii) ion-exchange process combined with gas permeable membrane contactor. The LCA showed that using a fertilizer solution containing the recovered nutrients was environmentally better in most of the impact categories evaluated. Ammonium nitrate was the most important environmental contributor when using the recovered fertilizer solution as a result of the high consumption of chemicals needed for its production. The TEA illustrated that the implementation of the nutrient recovery scheme in the WWTP featured a negative net present value (NPV), primarily attributed to the high consumption of chemicals (representing 30 % of the gross cost). However, the implementation of the nutrient recovery scheme in the WWTP could be economically favourable if the cost of ammonium nitrate and struvite increased to 0.68 and 0.58 €/kg, respectively. The results of this pilot-scale study highlight that nutrient recovery considering the whole value chain for fertilizer application can be an attractive full-scale alternative from a sustainability point of view.

Phosphorus recovery from wastewater via calcium phosphate precipitation: A critical review of methods, progress, and insights.

Phosphorus (P) is one of the important elements for human, animal, and plant life. Due to the development of the circular economy in recent years, the recovery of P from wastewater has received more attention. Recovery of P from domestic, industrial, and agricultural wastewater in the form of calcium phosphate (CaP) by precipitation/crystallization process presents a low-cost and effective method. Recovered CaP could be used as P fertilizer and for other industrial applications. This review summarizes the effects of supersaturation, pH, seed materials, calcium (Ca) source, and wastewater composition, on the precipitation/crystallization process. The recovery efficiency and value proposition of recovered CaP were assessed. This in-depth analysis of the literature reports identified the process parameters that are worth further optimization. The review also provides perspectives on future research needs on expanding the application field of recovered CaP and finding other more economical and environmentally friendly Ca sources.

MgFe-LDH@biochars for removing ammonia nitrogen and phosphorus from biogas slurry: Synthesis routes, composite performance, and adsorption mechanisms.

Layered double hydroxide-biochar composites (LDH@BCs) have been developed for ammonia nitrogen (AN) and phosphorus (P) removal from wastewater. Improvement of LDH@BCs was limited due to the lack of comparative evaluation based on LDH@BCs characteristics and synthetic methods and information on the adsorption properties of LDH@BCs for N and P from natural wastewater. In this study, MgFe-LDH@BCs were synthesized by three different co-precipitation procedures. The differences in physicochemical and morphological properties were compared. They were then employed to remove AN and P from biogas slurry. The adsorption performance of the three MgFe-LDH@BCs was compared and evaluated. Different synthesis procedures can significantly affect the physicochemical and morphological characteristics of MgFe-LDH@BCs. The LDH@BC composite fabricated through a novel method (labeled 'MgFe-LDH@BC1') has the largest specific surface area, Mg and Fe content, and excellent magnetic response performance. Moreover, the composite has the best adsorption property of AN and P from biogas slurry (30.0% and 81.8%, respectively). The main reaction mechanisms include memory effect, ion exchange, and co-precipitation. Applying 2% MgFe-LDH@BC1 saturated with AN and P adsorption from biogas slurry as a fertilizer substitute can substantially improve soil fertility and increase plant production by 139.3%. These results indicate that the facile LDH@BC synthesis method is an effective method to overcome the shortcomings of LDH@BC in practical application, and provide a basis for further exploration of the potential application of biochar based fertilizers in agriculture.